SCRYPTmail - Signature can not be verified

I noticed this warning appearing in my SCRYPTmail: "Signature can not be verified"

I think you are using the term "signature" in a different way than regular email users would expect.

Within the context of email, to me a signature is the (sometimes automatically added) block of text at the end of an email that contains the senders real name, email address, phone number, web site link, etc.